Human Rights Watch says the Laos government is not doing enough to investigate the disappearance of a prominent activist and is calling for the Association of Southeast Nations to intervene.

The rights group Wednesday said Laos authorities should end their silence on the case of Sombath Somphone, a sustainable development activist who went missing two months ago.

Sombath, 60, is widely thought to have been forcibly disappeared by authorities after security camera footage showed him being taken away from a police post in the city of Vientiane.

The government has promised an investigation, but has so far said nothing about his whereabouts or condition. It has suggested he was kidnapped for personal reasons or because of a business dispute.

HRW wants ASEAN and its human rights commission to intervene, saying the case is a "major test" for the regional body.

Last month, ASEAN representatives on a fact-finding visit to Laos criticized the government's investigation into the disappearance. The representatives said the government failed to provide answers to basic questions of the investigation and tried to deny police involvement.